Patrolling Alveolar Macrophages Conceal Bacteria from the Immune System to Maintain Homeostasis.

During respiration, humans breathe in more than 10,000 liters of non-sterile air daily, allowing some pathogens access to alveoli. Interestingly, alveoli outnumber alveolar macrophages (AMs), which favors alveoli devoid of AMs. If AMs, like most tissue macrophages, are sessile, then this numerical advantage would be exploited by pathogens unless neutrophils from the blood stream intervened. However, this would translate to omnipresent persistent inflammation. Developing in vivo real-time intravital imaging of alveoli revealed AMs crawling in and between alveoli using the pores of Kohn. Importantly, these macrophages sensed, chemotaxed, and, with high efficiency, phagocytosed inhaled bacterial pathogens such as P. aeruginosa and S. aureus, cloaking the bacteria from neutrophils. Impairing AM chemotaxis toward bacteria induced superfluous neutrophil recruitment, leading to inappropriate inflammation and injury. In a disease context, influenza A virus infection impaired AM crawling via the type II interferon signaling pathway, and this greatly increased secondary bacterial co-infection.

C-C chemokine receptor type 7 (CCR7) regulates hepatic CD8 + T cell homeostasis and response to acute liver injury.

BACKGROUND AND AIMS: Acute liver failure (ALF) is a rare but life-threatening condition, and DILI, particularly acetaminophen toxicity, is the leading cause of ALF. Innate immune mechanisms further perpetuate liver injury, while the role of the adaptive immune system in DILI-related ALF is unclear. APPROACH AND RESULTS: We analyzed liver tissue from 2 independent patient cohorts with ALF and identified hepatic T cell infiltration as a prominent feature in human ALF. CD8 + T cells were characterized by zonation toward necrotic regions and an activated gene expression signature. In murine acetaminophen-induced liver injury, intravital microscopy revealed zonation of CD8 + but not CD4 + T cells at necrotic areas. Gene expression analysis exposed upregulated C-C chemokine receptor 7 (CCR7) and its ligand CCL21 in the liver as well as a broadly activated phenotype of hepatic CD8 + T cells. In 2 mouse models of ALF, Ccr7-/- mice had significantly aggravated early-phase liver damage. Functionally, CCR7 was not involved in the recruitment of CD8 + T cells, but regulated their activation profile potentially through egress to lymphatics. Ccr7-/- CD8 + T cells were characterized by elevated expression of activation, effector, and exhaustion profiles. Adoptive transfer revealed preferential homing of CCR7-deficient CD8 + T cells to the liver, and depletion of CD8 + T cells attenuated liver damage in mice. CONCLUSIONS: Our study demonstrates the involvement of the adaptive immune system in ALF in humans and mice. We identify the CCR7-CCL21 axis as an important regulatory pathway, providing downstream protection against T cell-mediated liver injury.

Intravital imaging: dynamic insights into liver immunity in health and disease.

Inflammation is a critical component of most acute and chronic liver diseases. The liver is a unique immunological organ with a dense vascular network, leading to intense crosstalk between tissue-resident immune cells, passenger leucocytes and parenchymal cells. During acute and chronic liver diseases, the multifaceted immune response is involved in disease promoting and repair mechanisms, while upholding core liver immune functions. In recent years, single-cell technologies have unravelled a previously unknown heterogeneity of immune cells, reshaping the complexity of the hepatic immune response. However, inflammation is a dynamic biological process, encompassing various immune cells, orchestrated in temporal and spatial dimensions, and driven by multiorgan signals. Intravital microscopy (IVM) has emerged as a powerful tool to investigate immunity by visualising the dynamic interplay between different immune cells and their surroundings within a near-natural environment. In this review, we summarise the experimental considerations to perform IVM and highlight recent technological developments. Furthermore, we outline the unique contributions of IVM to our understanding of liver immunity. Through the lens of liver disease, we discuss novel immune-mediated disease mechanisms uncovered by imaging-based studies.

Mapping the hepatic immune landscape identifies monocytic macrophages as key drivers of steatohepatitis and cholangiopathy progression.

BACKGROUND AND AIMS: The progression of chronic liver diseases towards liver cirrhosis is accompanied by drastic tissue changes. This study combines elaborate transcriptomic and histological methods aiming at spatially resolving the hepatic immune microenvironment in NAFLD (including NASH, primary sclerosing cholangitis, primary biliary cholangitis, and severe alcoholic hepatitis). APPROACH AND RESULTS: Human liver samples were subjected to RNA-sequencing (n=225) and imaging cytometry (n=99) across 3 independent patient cohorts. Liver samples from alcoholic hepatitis and primary biliary cholangitis patients were used for comparison. Myeloid populations were further characterized in corresponding mouse models. Imaging, clinical, and phenotypical data were combined for multidimensional analysis. NAFLD/NASH and primary sclerosing cholangitis disease stages were associated with loss of parenchymal areas, increased ductular cell accumulation, and infiltration of immune cells. NASH patients predominantly exhibited myeloid cell accumulation, whereas primary sclerosing cholangitis patients additionally had pronounced lymphoid cell responses. Correlating to disease stage, both etiologies displayed intense IBA1 + CD16 low CD163 low macrophage aggregation in nonparenchymal areas, with a distinct spatial proximity to ductular cells. Mouse models revealed that disease-associated IBA1 + hepatic macrophages originated from bone marrow-derived monocytes. Using an unbiased, machine learning-based algorithm, IBA1 in combination with hepatocyte and ductular cell immunostaining-predicted advanced cirrhosis in human NASH, primary sclerosing cholangitis, and alcoholic hepatitis. CONCLUSIONS: Loss of hepatocytes and increased ductular reaction are tightly associated with monocyte-derived macrophage accumulation and represent the most prominent common immunological feature revealing the progression of NAFLD, primary sclerosing cholangitis, primary biliary cholangitis, and alcoholic hepatitis, suggesting IBA1 + CD163 low macrophages are key pathogenic drivers of human liver disease progression across diverse etiologies.

Ductular reaction-associated neutrophils promote biliary epithelium proliferation in chronic liver disease.

BACKGROUND & AIMS: Ductular reaction expansion is associated with poor prognosis in patients with advanced liver disease. However, the mechanisms promoting biliary cell proliferation are largely unknown. Here, we identify neutrophils as drivers of biliary cell proliferation and the defective wound-healing response. METHODS: The intrahepatic localization of neutrophils was evaluated in patients with chronic liver disease. Neutrophil dynamics were analyzed by intravital microscopy and neutrophil-labeling assays in DDC-treated mice. Neutrophil depletion or inhibition of recruitment was achieved using a Ly6g antibody or a CXCR1/2 inhibitor, respectively. Mice deficient in PAD4 (peptidyl arginine deiminase 4) and ELANE/NE (neutrophil elastase) were used to investigate the mechanisms underlying ductular reaction expansion. RESULTS: In this study we describe a population of ductular reaction-associated neutrophils (DRANs), which are in direct contact with biliary epithelial cells in chronic liver diseases and whose numbers increased in parallel with disease progression. We show that DRANs are immobilized at the site of ductular reaction for a prolonged period of time. In addition, liver neutrophils display a unique phenotypic and transcriptomic profile, showing a decreased phagocytic capacity and increased oxidative burst. Depletion of neutrophils or inhibition of their recruitment reduces DRANs and the expansion of ductular reaction, while mitigating liver fibrosis and angiogenesis. Mechanistically, neutrophils deficient in PAD4 and ELANE abrogate neutrophil-induced biliary cell proliferation, thus indicating the role of neutrophil extracellular traps and elastase release in ductular reaction expansion. CONCLUSIONS: Overall, our study reveals the accumulation of DRANs as a hallmark of advanced liver disease and a potential therapeutic target to mitigate ductular reaction and the maladaptive wound-healing response. IMPACT AND IMPLICATIONS: Our results indicate that neutrophils are highly plastic and can have an extended lifespan. Moreover, we identify a new role of neutrophils as triggers of expansion of the biliary epithelium. Overall, the results of this study indicate that ductular reaction-associated neutrophils (or DRANs) are new players in the maladaptive tissue-healing response in chronic liver injury and may be a potential target for therapeutic interventions to reduce ductular reaction expansion and promote tissue repair in advanced liver disease.

Immune mechanisms linking metabolic injury to inflammation and fibrosis in fatty liver disease - novel insights into cellular communication circuits.

Non-alcoholic fatty liver disease (NAFLD) is the most prevalent chronic liver disease and is emerging as the leading cause of cirrhosis, liver transplantation and hepatocellular carcinoma (HCC). NAFLD is a metabolic disease that is considered the hepatic manifestation of the metabolic syndrome; however, during the evolution of NAFLD from steatosis to non-alcoholic steatohepatitis (NASH), to more advanced stages of NASH with liver fibrosis, the immune system plays an integral role. Triggers for inflammation are rooted in hepatic (lipid overload, lipotoxicity, oxidative stress) and extrahepatic (gut-liver axis, adipose tissue, skeletal muscle) systems, resulting in unique immune-mediated pathomechanisms in NAFLD. In recent years, the implementation of single-cell RNA-sequencing and high dimensional multi-omics (proteogenomics, lipidomics) and spatial transcriptomics have tremendously advanced our understanding of the complex heterogeneity of various liver immune cell subsets in health and disease. In NAFLD, several emerging inflammatory mechanisms have been uncovered, including profound macrophage heterogeneity, auto-aggressive T cells, the role of unconventional T cells and platelet-immune cell interactions, potentially yielding novel therapeutics. In this review, we will highlight the recent discoveries related to inflammation in NAFLD, discuss the role of immune cell subsets during the different stages of the disease (including disease regression) and integrate the multiple systems driving inflammation. We propose a refined concept by which the immune system contributes to all stages of NAFLD and discuss open scientific questions arising from this paradigm shift that need to be unravelled in the coming years. Finally, we discuss novel therapeutic approaches to target the multiple triggers of inflammation, including combination therapy via nuclear receptors (FXR agonists, PPAR agonists).

Tacrolimus Impairs Kupffer Cell Capacity to Control Bacteremia: Why Transplant Recipients Are Susceptible to Infection.

BACKGROUND AND AIMS: Kupffer cells (KCs) are the resident intravascular phagocyte population of the liver and critical to the capture and killing of bacteria. Calcineurin/nuclear factor of activated T cells (NFAT) inhibitors (CNIs) such as tacrolimus are used to prevent rejection in solid organ transplant recipients. Although their effect on lymphocytes has been studied extensively, there are limited experimental data about if and how CNIs shape innate immunity, and whether this contributes to the higher rates of infection observed in patients taking CNIs. APPROACH AND RESULTS: Here, we investigated the impact of tacrolimus treatment on innate immunity and, more specifically, on the capability of Kupffer cells (KCs) to fight infections. Retrospective analysis of data of >2,700 liver transplant recipients showed that taking calcineurin inhibitors such as tacrolimus significantly increased the likelihood of Staphylococcus aureus infection. Using a mouse model of acute methicillin-resistant S. aureus (MRSA) bacteremia, most bacteria were sequestered in the liver and we found that bacteria were more likely to disseminate and kill the host in tacrolimus-treated mice. Using imaging, we unveiled the mechanism underlying this observation: the reduced capability of KCs to capture, phagocytose, and destroy bacteria in tacrolimus-treated animals. Furthermore, in a gene expression analysis of infected KCs, the triggering receptor expressed on myeloid cells 1 (TREM1) pathway was the one with the most significant down-regulation after tacrolimus treatment. TREM1 inhibition likewise inhibited KC bacteria capture. TREM1 levels on neutrophils as well as the overall neutrophil response after infection were unaffected by tacrolimus treatment. CONCLUSIONS: Our results indicate that tacrolimus treatment has a significant impact directly on KCs and on TREM1, thereby compromising their capacity to fend off infections.

Nuclear Receptors Linking Metabolism, Inflammation, and Fibrosis in Nonalcoholic Fatty Liver Disease.

Nonalcoholic fatty liver disease (NAFLD) and its progressive form nonalcoholic steatohepatitis (NASH) comprise a spectrum of chronic liver diseases in the global population that can lead to end-stage liver disease and hepatocellular carcinoma (HCC). NAFLD is closely linked to the metabolic syndrome, and comorbidities such as type 2 diabetes, obesity and insulin resistance aggravate liver disease, while NAFLD promotes cardiovascular risk in affected patients. The pathomechanisms of NAFLD are multifaceted, combining hepatic factors including lipotoxicity, mechanisms of cell death and liver inflammation with extrahepatic factors including metabolic disturbance and dysbiosis. Nuclear receptors (NRs) are a family of ligand-controlled transcription factors that regulate glucose, fat and cholesterol homeostasis and modulate innate immune cell functions, including liver macrophages. In parallel with metabolic derangement in NAFLD, altered NR signaling is frequently observed and might be involved in the pathogenesis. Therapeutically, clinical data indicate that single drug targets thus far have been insufficient for reaching patient-relevant endpoints. Therefore, combinatorial treatment strategies with multiple drug targets or drugs with multiple mechanisms of actions could possibly bring advantages, by providing a more holistic therapeutic approach. In this context, peroxisome proliferator-activated receptors (PPARs) and other NRs are of great interest as they are involved in wide-ranging and multi-organ activities associated with NASH progression or regression. In this review, we summarize recent advances in understanding the pathogenesis of NAFLD, focusing on mechanisms of cell death, immunometabolism and the role of NRs. We outline novel therapeutic strategies and discuss remaining challenges.

Monocytes as Potential Mediators of Pathogen-Induced T-Helper 17 Differentiation in Patients With Primary Sclerosing Cholangitis (PSC).

BACKGROUND AND AIMS: T cells from patients with primary sclerosing cholangitis (PSC) show a prominent interleukin (IL)-17 response upon stimulation with bacteria or fungi, yet the reasons for this dominant T-helper 17 (Th17) response in PSC are not clear. Here, we analyzed the potential role of monocytes in microbial recognition and in skewing the T-cell response toward Th17. APPROACH AND RESULTS: Monocytes and T cells from blood and livers of PSC patients and controls were analyzed ex vivo and in vitro using transwell experiments with cholangiocytes. Cytokine production was measured using flow cytometry, enzyme-linked immunosorbent assay, RNA in situ hybridization, and quantitative real-time PCR. Genetic polymorphisms were obtained from ImmunoChip analysis. Following ex vivo stimulation with phorbol myristate acetate/ionomycin, PSC patients showed significantly increased numbers of IL-17A-producing peripheral blood CD4+ T cells compared to PBC patients and healthy controls, indicating increased Th17 differentiation in vivo. Upon stimulation with microbes, monocytes from PSC patients produced significantly more IL-1ß and IL-6, cytokines known to drive Th17 cell differentiation. Moreover, microbe-activated monocytes induced the secretion of Th17 and monocyte-recruiting chemokines chemokine (C-C motif) ligand (CCL)-20 and CCL-2 in human primary cholangiocytes. In livers of patients with PSC cirrhosis, CD14hiCD16int and CD14loCD16hi monocytes/macrophages were increased compared to alcoholic cirrhosis, and monocytes were found to be located around bile ducts. CONCLUSIONS: PSC patients show increased Th17 differentiation already in vivo. Microbe-stimulated monocytes drive Th17 differentiation in vitro and induce cholangiocytes to produce chemokines mediating recruitment of Th17 cells and more monocytes into portal tracts. Taken together, these results point to a pathogenic role of monocytes in patients with PSC.

TNF-Producing Th1 Cells Are Selectively Expanded in Liver Infiltrates of Patients with Autoimmune Hepatitis.

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease that is believed to be driven by a CD4+ T cell response to liver Ags. However, the pathogenic function of CD4+ effector T cells in AIH is not fully understood. To characterize liver-infiltrating lymphocytes in AIH, we determined the cytokine production of infiltrating cells obtained from biopsy material by quantitative RT-PCR and flow cytometry. A cytokine quantitiative RT-PCR array of AIH specimens revealed that TNF was the most strongly upregulated cytokine, as compared with control livers. To confirm this finding, we determined the frequencies of TNF-producing CD4+ T cells in peripheral blood and in liver biopsy specimens in comparison with those of CD4+ T cells producing IFN-γ or IL-17. In AIH, TNF-producing CD4+ T cells were significantly expanded, both in blood and liver, whereas IL-17-producing CD4+ T cells were not. However, the majority of the TNF-producing CD4+ T cells in AIH also produced IFN-γ, suggesting that TNF producers might represent a pathogenic activation state of Th1 cells. Ag-specific stimulation of PBMC from AIH patients with the AIH-associated autoantigen SEPSECS resulted in significant TNF production only in patients manifesting SLA/LP autoantibodies targeting SEPSEC but not in healthy individuals who do not manifest this reactivity. Taken together, our findings indicated that TNF-producing CD4+ T cells are expanded in AIH, both in blood and in liver. TNF-producing CD4+ T cells in AIH seem to be aberrantly activated Th1 cells. Our findings provide a rationale for therapeutic efforts using TNF blockade in AIH.

Metamizole: An underrated agent causing severe idiosyncratic drug-induced liver injury.

AIMS: Drug-induced liver injury (DILI) is a heterogenous entity leading to liver damage. We have analysed the frequency, biochemical and histological patterns and clinical courses of DILI cases due to metamizole at our tertiary care centre in Hamburg, Germany. METHODS: Consecutive patients with DILI who presented to our clinic were analysed retrospectively. Causes of acute hepatitis other than DILI were excluded. RESULTS: In total, 154 DILI cases were admitted to our centre from 2008 to 2017. After phenprocoumon, metamizole was the second most frequent putative agent causing DILI (23 of all 154 DILI cases, 14,9%). The biochemical pattern on admission of metamizole-induced DILI cases was hepatocellular with median levels of alanine transaminase (779 U/L, 64-3532 U/L) by far exceeding median alkaline phosphatase levels (131 U/L, 42-578 U/L). In 17 of the 23 cases (74%) liver biopsy was performed. Moderate to severe inflammatory histological activity and severe centrilobular necrosis (>30%) was present in 76.5 and 35.3%, respectively. Metamizole was involved in 2 DILI cases progressing to acute liver failure, then receiving liver transplantation and still alive at time of assessment. Our data were supported by re-exposure in 4 patients. Furthermore, a database search for metamizole-induced liver injury in the European Medicines Agency's database identified about 300 reports on suspected metamizole-induced DILI in Europe. CONCLUSION: Elevation of liver enzymes or acute liver failure are not mentioned in the German drug label of metamizole as potential side effects. Our study reveals that in Germany and Europe, metamizole is a frequent and underrated agent causing DILI.

Usefulness of biochemical remission and transient elastography in monitoring disease course in autoimmune hepatitis.

BACKGROUND & AIMS: Liver fibrosis regression but also progression may occur in patients with autoimmune hepatitis (AIH) under treatment. There is a need for non-invasive surrogate markers for fibrosis development in AIH to better guide immunosuppressive treatment. The aims of the study were to assess the impact of complete biochemical remission defined as normalisation of aminotransferases and IgG on histological activity and fibrosis development, and the value of repeat transient elastography (TE) measurement for monitoring disease progression in AIH. METHODS: A total of 131 liver biopsies from 60 patients with AIH and more than 900 TE from 125 patients with AIH, 130 with primary biliary cholangitis (PBC) and 100 with primary sclerosing cholangitis (PSC), were evaluated. Time intervals between TE were at least 12 months. Patients with AIH were treated for at least six months at first TE. RESULTS: In contrast to PBC and PSC, a decrease of liver stiffness (LS) was observed in the whole group of patients with AIH (-6.2%/year; 95% CI -12.6% to -0.2%; p = 0.04). The largest decrease of LS was observed in patients with severe fibrosis at baseline (F4: -11.7%/year; 95% CI -19% to -3.5%; p = 0.006). Complete biochemical remission was strongly linked to regression of LS ("remission": -7.5%/year vs. "no remission": +1.7%/year, p <0.001). Similarly, complete biochemical remission predicted low histological disease activity and was the only independent predictor for histological fibrosis regression (relative risk3.66; 95% CI1.54-10.2; p = 0.001). Patients with F3/F4-fibrosis, who remained in biochemical remission showed a considerable decrease of fibrosis stage (3.7 ±â€¯0.5 to 1.8 ±â€¯1.7; p = 0.007) on histological follow-up. CONCLUSIONS: This study demonstrates that complete biochemical remission is a reliable predictor of a good prognosis in AIH and leads to fibrosis regression that can be monitored by TE. LAY SUMMARY: Autoimmune hepatitis is an inflammatory disease of the liver, which often progresses to cirrhosis if left untreated or in the case of insufficient treatment response. Current guidelines have defined biochemical remission (normalisation of biochemical markers for liver inflammation) as a major goal in the treatment of AIH. However, data on the prognostic relevance of this definition are scarce. Herein, we demonstrate that the current definition of biochemical remission is a reliable surrogate for low disease activity on histological assessment and for a beneficial long-term disease course. In addition, we establish transient elastography, a non-invasive ultrasound-based method of measuring scarring of liver tissue, as a reliable tool to monitor disease course in AIH.

Efficacy and Limitations of Budesonide as a Second-Line Treatment for Patients With Autoimmune Hepatitis.

BACKGROUND & AIMS: Many patients with autoimmune hepatitis (AIH) develop steroid-specific side effects or require doses of steroids that are unacceptable for long-term treatment. We investigated the efficacy of budesonide as an alternative steroid for patients previously treated with prednisolone who developed side effects or were unable to reduce their dose of prednisolone below acceptable levels. We also report the effects of more than 12 months of budesonide treatment in a large cohort of patients with AIH. METHODS: We performed a retrospective analysis of data from 60 patients (51 female) with AIH who were treated initially with prednisolone (mean time, 47 mo) but then switched to budesonide, managed at a single center in Germany from 2001 through June 2016. Patients were evaluated after 6 months, 12 months, 24 months, 36 months, and at the last follow-up evaluation; response to treatment with budesonide was assessed based on normal serum levels of aminotransferases and IgG (biochemical response). RESULTS: Thirty patients were switched to budesonide therapy because of prednisolone-induced side effects and 30 patients switched because of prednisolone dependency. Overall, a biochemical response was detected in 55% of patients after 6 months of budesonide treatment, in 70% after 12 months, and in 67% after 24 months. At the last follow-up evaluation (mean time, 63 mo) 23 patients (38%) still were receiving budesonide treatment. Fifteen patients (25%) had switched back to prednisolone therapy because of insufficient response to budesonide or its side effects. Fifteen patients with osteopenia at the beginning of budesonide treatment were followed up and evaluated by dual-energy X-ray absorptiometry. After a median of 24 months of budesonide treatment, bone mineral density had improved in 6 patients, remained stable in 8 patients, and worsened in 1 patient. CONCLUSIONS: We performed a retrospective analysis of patients with AIH that confirmed the therapeutic value of budesonide beyond 12 months of treatment in patients who are intolerant to or dependent on prednisolone. Although budesonide-induced side effects appear to be mild in real life, effectiveness was limited in a considerable proportion of patients; close monitoring is advised.

Potential impact of screening for fatty liver disease by transient elastography with liver stiffness and controlled attenuation parameter measurements: a pilot study.

Background The prevalence of chronic liver diseases is high in developed countries, and the leading causes are amenable to prevention. The German Lebertag is to increase awareness of the burden of chronic liver diseases in the general public. We performed a pilot study using transient elastography with liver stiffness measurement (LSM) and the controlled attenuation parameter (CAP) as a screening tool for previously unrecognized liver diseases. Patients and methods LSM and CAP was performed in 60 individuals, and participants filled in a questionnaire reporting basic characteristics and past medical history. Results Median LSM and CAP values were within the normal range. Participants with self-reported diabetes mellitus had significantly elevated LSM (p = 0.02) and CAP values (p = 0.002). Participants with a BMI > 30 kg/m2 or dyslipidemia had significantly elevated CAP values (p = 0.007 and p = 0.01, respectively) with normal LSM values. Overall, 35 % of participants had elevated CAP values, indicating a high prevalence of hepatic steatosis. Discussion In a German pilot study, diabetes mellitus was a key risk factor for increased LSM and CAP values. Prevalence of steatosis was high and comparable to other Western countries. Transient elastography is a valuable tool to identify patients with increased risk for metabolic liver diseases. In people without risk factors, LSM and CAP values were within the normal range, indicating that screening for chronic liver injury was not warranted.

Transient elastography in autoimmune hepatitis: Timing determines the impact of inflammation and fibrosis.

BACKGROUND & AIMS: There is an unmet need for the non-invasive monitoring of fibrosis progression in patients with autoimmune hepatitis (AIH). The aim of this study was to assess the diagnostic performance of transient elastography in patients with AIH and to investigate the impact of disease activity on its diagnostic accuracy. METHODS: Optimal cut-offs were defined in a prospective pilot study (n=34) and the diagnostic performance of transient elastography validated in an independent second cohort (n=60). To explore the impact of disease activity on liver stiffness, patients were stratified according to biochemical response and the time interval between start of immunosuppression and transient elastography. RESULTS: Liver stiffness strongly correlated with histological fibrosis stage (pilot study: ρ=0.611, p<0.001; validation cohort: ρ=0.777, p<0.0001). ROC curves defined an area under the receiver operating curve of 0.95 for diagnosing cirrhosis at the optimal cut-off of 16kPa. The performance of transient elastography was impaired when patients were analysed in whom transient elastography was performed within 3months from start of treatment. In this setting, liver stiffness correlated with histological grading (ρ=0.558, p=0.001), but not with staging. In contrast, using the cut-off of 16kPa, the accuracy for diagnosing cirrhosis was excellent in patients treated for 6months or longer (area under the receiver operating curve 1.0). CONCLUSIONS: Liver inflammation has a major impact on liver stiffness in the first months of AIH treatment. However, transient elastography has an excellent diagnostic accuracy for separating severe from non-severe fibrosis after 6months of immunosuppressive treatment. LAY SUMMARY: Transient elastography is a special ultrasound scan, which assesses liver stiffness as a surrogate marker for liver fibrosis/scarring. Transient elastography has been shown to be a reliable non-invasive method to assess liver fibrosis in various chronic liver diseases, it takes less than 5min and has a high patient acceptance. The current study validated for the first time this technique in a large cohort of patients with autoimmune hepatitis (AIH) and demonstrates that it is a reliable tool to detect liver fibrosis in treated AIH. For the monitoring of potential disease progression under treatment, the validation of liver stiffness as non-invasive marker of liver fibrosis will greatly improve patient care in autoimmune hepatitis.

No Evidence That Azathioprine Increases Risk of Cholangiocarcinoma in Patients With Primary Sclerosing Cholangitis.

BACKGROUND & AIMS: Patients with primary sclerosing cholangitis (PSC) are at increased risk for developing cholangiocarcinoma (CCA). Patients with PSC also can have inflammatory bowel diseases (IBDs) or features of autoimmune hepatitis (AIH), and therefore are treated with azathioprine. Azathioprine has been associated with an increased risk for malignancy, therefore we investigated whether azathioprine use affects the risk of CCA in persons with PSC. METHODS: We performed a retrospective study of well-defined patients with PSC using data collected from 3 large-volume, tertiary care centers in Germany and Norway. We analyzed data from 638 patients (70% men; 5900 patient-years of follow-up evaluation); 91 patients had received azathioprine therapy (considered to be effective at 90 days after first intake). Risk analysis was performed using the Cox proportional hazard model when risks competing with study end points were present. RESULTS: Of patients who received azathioprine treatment, 3.3% developed CCA, compared with 6.8% of patients without azathioprine treatment. However, azathioprine did not significantly affect the risk for CCA (hazard ratio, 0.96; 95% confidence interval, 0.29-3.13; P = .94). The only factor associated with an increased risk of CCA was age 35 years or older at PSC diagnosis (hazard ratio, 3.87; 95% confidence interval, 1.96-7.67; P < .01). Patient sex, concomitant IBD, or AIH did not affect the risk of CCA. Overall, the cumulative 10-year incidence of CCA was 4.6% and the cumulative 15-year incidence was 7.7%. CONCLUSIONS: A retrospective analysis of patients with PSC treated at tertiary centers in Europe found no evidence that azathioprine significantly affects the risk of CCA. Azathioprine therefore should not be withheld from patients with PSC and concomitant IBD and/or AIH.

Reduced FOXP3(+) regulatory T cells in patients with primary sclerosing cholangitis are associated with IL2RA gene polymorphisms.

BACKGROUND & AIMS: Recently, genome wide association studies in primary sclerosing cholangitis (PSC) revealed associations with gene polymorphisms that potentially could affect the function of regulatory T cells (Treg). The aim of this study was to investigate Treg in patients with PSC and to associate their numbers with relevant gene polymorphisms. METHODS: Treg frequency in blood was assessed by staining for CD4(+)CD25(high)FOXP3(+)CD127(low) lymphocytes and determination of Treg-specific FOXP3 gene locus demethylation. Single nucleotide polymorphisms (SNP) in the interleukin-2 receptor alpha (IL2RA), the interleukin-2 (IL2) and interleukin-21 (IL21) gene locus were analysed. Liver biopsies taken at the time of diagnosis were stained for FOXP3 and CD3. Treg function was assessed in a CFSE-based suppression assay. RESULTS: The frequency of Treg in peripheral blood of PSC patients was significantly decreased. We confirmed this finding by demonstrating a reduction of non-methylated DNA in the Treg-specific demethylated FOXP3 gene region of peripheral blood cells in PSC patients. Reduced peripheral Treg numbers were significantly associated with homozygosity for the major allele of the SNP "rs10905718" in the IL2RA gene. Intrahepatic FOXP3(+) cell numbers at the time of initial diagnosis were decreased in PSC as compared to PBC. In addition to reduced numbers, the suppressive capacity of Treg isolated from PSC patients seemed to be impaired as compared to healthy controls. CONCLUSIONS: Our findings indicate that Treg impairment may play a role in the immune dysregulation observed in PSC. Reduced Treg numbers in patients with PSC are associated with polymorphisms in the IL2RA gene.

Hepatic C-X-C chemokine receptor type 6-expressing innate lymphocytes limit detrimental myeloid hyperactivation in acute liver injury.

BACKGROUND: Acute liver failure (ALF) is characterized by rapid clinical deterioration and high mortality. Acetaminophen (APAP or paracetamol) overdose is a leading cause of ALF, resulting in hepatocellular necrosis with subsequent inflammation, inflicting further liver damage. Infiltrating myeloid cells are early drivers of liver inflammation. However, the role of the abundant population of liver-resident innate lymphocytes, which commonly express the chemokine receptor CXCR6, is incompletely understood in ALF. METHODS: We investigated the role of CXCR6-expressing innate lymphocytes using the model of acute APAP toxicity in mice deficient in CXCR6 (Cxcr6gfp/gfp). RESULTS: APAP-induced liver injury was strongly aggravated in Cxcr6gfp/gfp mice compared with wild-type counterparts. Immunophenotyping using flow cytometry revealed a reduction in liver CD4+T cells, natural killer (NK) cells, and most prominently, NKT cells, whereas CXCR6 was dispensable for CD8+ T-cell accumulation. CXCR6-deficient mice exhibited excessive neutrophil and inflammatory macrophage infiltration. Intravital microscopy revealed dense cellular clusters of neutrophils in necrotic liver tissue, with higher numbers of clustering neutrophils in Cxcr6gfp/gfp mice. Gene expression analysis linked hyperinflammation in CXCR6 deficiency to increased IL-17 signaling. Although reduced in overall numbers, CXCR6-deficient mice had a shift in NKT cell subsets with increased RORγt-expressing NKT17 cells as a likely source of IL-17. In patients with ALF, we found a prominent accumulation of IL-17-expressing cells. Accordingly, CXCR6-deficient mice lacking IL-17 (Cxcr6gfp/gfpx Il17-/-) had ameliorated liver damage and reduced inflammatory myeloid infiltrates. CONCLUSIONS: Our study identifies a crucial role of CXCR6-expressing liver innate lymphocytes as orchestrators in acute liver injury containing IL-17-mediated myeloid cell infiltration. Hence, strengthening the CXCR6-axis or downstream inhibition of IL-17 could yield novel therapeutics in ALF.